A protein which binds retinol in vivo has been discovered in rat. It is distinctly different from the other well-known binding proteins for vitamin A compounds previously described. The new protein is present in intestine and may have a role in absorption of vitamin A. Vitamin A is essential not only for vision but for the maintenance of most, if not all, of the epithelial tissues of the body. Research on this protein is designed to improve the purification procedure, continue its characterization, produce antibodies specific for the two forms of the protein observed, determine the distribution of the protein with respect to species, tissue, vitamin A status, and age. Its degree of saturation with retinol will be examined as affected by dietary intake of vitamin A. The protein will be examined for ability to reduce retinol, to esterify retinol or to facilitate its esterification with known enzyme systems. The primary laboratory animal is rat.